Method and machine for manufacturing a heat exchanger block, fins for manufacturing a heat exchanger block, and heat exchanger block

ABSTRACT

This invention relates to a method and machine for manufacturing a heat exchanger block, to fins for manufacturing a heat exchanger block, and to a heat exchanger block. There is provided a method of manufacturing a heat exchanger block( 12 ) comprising a number of tubes ( 16 ) and a number of fins ( 14; 214   a,    214   b;    314   a,   314   b ), neighbouring fins being separated by a predetermined spacing by way of spacer means ( 52; 52   a,    52   b ), the method including the steps of: locating a predetermined number of tubes in a chosen array; locating a number of fins adjacent an end of the tubes; fitting the fins onto the tubes; and vibrating the tubes and/or the fins during the step of fitting the fins onto the tubes. There is also provided a fin ( 14; 214   a,    214   b;    314   a,    314   b ) for a heat exchanger block ( 12 ), the fin having integral spacer means( 52; 52   a,    52   b ) whereby the spacer means of one fin can engage the neighbouring fin and determine the spacing therebetween, the fin having a number of apertures ( 40 ) to receive a number of tubes ( 16 ), the spacer means being located at a distance from the apertures.

FIELD OF THE INVENTION

This invention relates to a method and machine for manufacturing a heatexchanger block, to fins for manufacturing a heat exchanger block, andto a heat exchanger block. The invention describes certain improvementsover the method and apparatus of our copending applicationPCT/GB2011/052054.

BACKGROUND OF THE INVENTION

Often it is necessary to cool a working fluid, and it is known for thispurpose to use a heat exchanger. Heat exchangers are made in manydifferent sizes, are used with many different working fluids, andutilise many different fluids as the coolant. The present invention isdirected primarily at heat exchangers in which the working fluid is aliquid, typically water or oil, and in which the coolant is a gas,typically air. Such heat exchangers are widely used on industrialcompressors for example, but the invention is also expected to haveutility for other air-cooled heat exchangers. Also, the use of theinvention for other heat exchangers, including those for which thecoolant is another fluid such as water, is not excluded.

Heat exchangers in which the working fluid is a liquid usually comprisea number of tubes suspended between two tube plates, though it is knownto use U-shaped tubes with each tube connected at opposite ends to asingle tube plate. Typically, the working fluid flows through the tubes,whilst the coolant passes around and between the tubes, the workingfluid giving up latent heat (by way of the tubes) to the coolant flowingaround the tubes.

Each tube will typically carry a number of external fins, sometimescalled “extended surface members”, which are mechanically coupled to orintegral with the respective tube. The fins increase the availablesurface area for heat transfer, but also cause an increase in thepressure drop as the coolant passes between and around the tubes. Theheat exchanger designer will typically seek to increase the density ofthe fins so as to increase the heat exchange, without exceeding amaximum permissible pressure drop.

Often, each fin will engage more than one tube, with the finssubstantially filling the space between the tubes. During themanufacture of a heat exchanger the manufacturer will often makesub-assemblies comprising a chosen number of tubes fitted with a chosennumber of fins. These sub-assemblies are referred to herein as heatexchanger blocks, and are sometimes called fin blocks. The heatexchanger is assembled by securing the desired number of heat exchangerblocks to the tube plates.

It is a requirement for industrial heat exchangers to minimise the costof manufacture. The time taken to manufacture the heat exchangers, andin particular the time for which the manufacturing or assembly line isutilised for a particular heat exchanger, is a significant proportion ofthe cost of manufacture. Most heat exchanger manufacturers thereforewish to reduce the time taken to manufacture their heat exchangers, andalso seek alternative materials and methods in order to reduce themanufacturing cost.

Another requirement for industrial heat exchangers is to minimise theirsize and weight without compromising their heat exchange performance.Whilst a larger heat exchanger will typically provide a greater rate ofheat exchange from the working fluid to the coolant, heat exchangerdesigners typically seek to minimise the size and weight of the heatexchanger so as to increase the portability of the heat exchanger, andto make it easier to package the heat exchanger alongside its relatedcomponentry.

DESCRIPTION OF THE PRIOR ART

Heat exchangers are most often constructed from metallic materials, i.e.metallic fins fitted to metallic tubes. Metals are commonly used becauseof their good thermal transfer properties. To secure a fin to the tubeit is known to provide an aperture in the fin and to weld or braze thefin onto the tube. This method of manufacture suffers from severalsignificant disadvantages. Firstly, the materials which can be used forthe tubes and the fins are limited to those which can be welded orbrazed. Secondly, the grade of the materials used, such as for examplethe minimum wall thickness of the tube, is determined by the requirementto withstand the welding or brazing operation (so that a relativelythick tube may need to be used, whereas a thinner tube would enhance theheat exchange performance). Thirdly, the welding or brazing operationraises the temperature of the tubes and fins sufficiently to heat treatthe materials, the final product being softer than the startingmaterials—the starting materials must therefore be chosen so that thefinal product meets the desired material requirements. Fourthly, therequirement for a welding or brazing operation adds time and cost to themanufacture of the heat exchanger.

In an alternative known method of manufacture the fins are initiallylocated as a loose fit upon the tubes and the tubes are thereaftermechanically expanded by a specialised expanding machine into thermalengagement with the fins. This method of manufacture also has a numberof significant disadvantages. The first disadvantage is shared with thefirst method stated above, namely that the material of the tube inparticular is limited to those which can be mechanically expanded. Thesecond disadvantage is also shared with the first method as statedabove, namely that the minimum thickness of the tubes is determined bythe requirement for expansion—very thin tubes, which might beparticularly suitable for heat exchangers, cannot be used if there is apossibility that they would split during the expansion process, or besufficiently weakened by the expansion process to fail in service. Thethird disadvantage is that the fins are sometimes pushed along the tubesduring the expansion process, so that the resulting fin spacing ordensity is not always consistent along the length of the tubes—this canhave a significant effect upon both the heat exchanger performance andthe pressure drop of the coolant. One arrangement using this methodutilises fins with integral spacer means. The integral spacer meansavoids the third disadvantage, but the first and second disadvantagespresent a significant concern to heat exchanger manufacturers who mightwish to use this method.

An alternative and improved method of mounting fins upon heat exchangertubes (and thereby manufacturing a heat exchanger block) is described inWO96/35093. That document discloses a tube finning machine in which finscan be pressed onto tubes by a linear motor, which has the accuracyrequired to ensure that the fins are accurately and consistently spaced.Since no welding or brazing is required, and no expansion of the tube isrequired, the materials of the tubes and/or fins is less limited thanthe earlier-described methods, and the machine and method can be usedwith a mixture of different materials for the tubes and/or fins in asingle heat exchanger block.

The apertures in the fins described in WO96/35093 are closely-sized tomatch the outside diameter of the tubes. The apertures in manyembodiments are formed with collars which engage the tubes in use andenhance the heat exchange performance. Whilst it is primarily intendedthat the linear motor will determine the position of each of the fins,it is often desired that the collar of one fin engage the collar of theadjacent fin, and it is disclosed that in some heat exchangers the finspacing can be determined by the engagement of adjacent fins. Since thefin spacing is usually predetermined by the heat exchange and pressuredrop required, in such embodiments the length of the collars is designedto provide the desired fin spacing.

Another tube finning machine for manufacturing heat exchanger blocks isdisclosed in WO02/30591. That document discloses the use of a cartridgemechanism into which a large number of fins can be loaded, and which canthereafter be pressed onto the tubes together. This machine and methodcan provide a considerable reduction in the time taken to manufacture,and therefore the manufacturing cost of, certain heat exchanger blocks.

DISCLOSURE OF THE INVENTION

The present invention seeks to provide a method and machine for mountingfins upon heat exchanger tubes which improves further on theefficiencies afforded by the disclosures of WO96/35093 and WO02/30591.The invention also provides a fin for use in manufacturing a heatexchanger block, and a heat exchanger block.

According to the invention, there is provided a method of manufacturinga heat exchanger block comprising a number of tubes and a number offins, neighbouring fins being separated by a predetermined spacing byway of spacer means, the method including the steps of locating a numberof fins and fitting the fins onto the tubes, the method including thestep of vibrating the tubes and/or the fins during the step of locatingthe fins upon the tubes.

In preferred embodiments of the method, the tubes are oriented withtheir longitudinal axes substantially vertical whereby gravity acts tomove the fins along the tubes to their required position. The mechanicalengagement between the fins and the tubes is sufficiently large toprovide the required heat transfer between the tubes and the fins, andyet permits the vibration to move the fins along the tubes under theforce of gravity alone.

The invention can, however, alternatively be utilised with the tubes atanother angle, including substantially horizontal, with the vibrationacting to assist the force provided by a pressing machine. In thesealternative embodiments, the fins can be moved by the pressing machinerelative to the stationary tubes, or the tubes can be moved relative tothe stationary fins, or both the fins and tubes can be moved, asdesired, the vibration reducing the force which is required to beprovided by the pressing machine, or increasing the number of fins whichcan be pressed by the pressing machine.

The present invention shares the benefits of the prior art disclosuresof WO96/35093 and WO02/30591 in not requiring a welding, brazing orexpansion step, and therefore enables the use of a greater range ofmaterials for the fins and tubes. Nevertheless, the present inventiondoes not exclude the use of a brazing or welding step, or otherwisesecuring adjacent fins together, if that is desired in a particular heatexchanger block. In one example, a chosen number of fins can be securedtogether by brazing or gluing prior to their location upon the tubes.

The invention also provides a fin for a heat exchanger block, the finhaving integral spacer means whereby the spacer means of one fin canengage the neighbouring fin and determine the spacing therebetween, thefin having a number of apertures to receive a number of tubes, thespacer means being located at a distance from the apertures.

Accordingly, the fins of the present invention differ from the fins ofWO96/35093 in providing the spacer means away from the tubes, and inparticular separate from any collar which surrounds an aperture andengages the tube. Thus, it is known that in embodiments in which thecollars act to space the fins, the collar of one fin can interlock withthe collar of an adjacent fin, increasing the force required to pressthe fins onto the tubes. The present invention avoids the possibility ofthe collars interlocking by providing spacer means remote from theapertures, which therefore do not engage the tubes.

The integral spacer means allows a number of fins to be located upon thetubes together, each fin being supported by a spacer means (andconsequently by the other fins). The spacer means maintains the desiredseparation between adjacent fins as the fins are moved onto the tubes,and also in the assembled heat exchanger block.

Accordingly, since the fin spacing or density in the assembled heatexchanger block is determined by the spacer means, there is norequirement to use a linear motor or other machine which can preciselyposition each fin.

Desirably, a number of heat exchanger blocks are assembled into a heatexchanger by securing the heat exchanger blocks to respective tubeplates. The heat exchanger blocks may comprise a single row of tubesinterconnected by a number of fins, or may comprise an array of tubes.If desired, the heat exchanger block may comprise all of the tubes of acomplete heat exchanger core (such as the finned core of a compressorcooler for example).

Alternatively, making a heat exchanger from a number of heat exchangerblocks which comprise a single row of tubes and their respective fins isparticularly cost effective, as the heat exchanger blocks can be made instandard dimensions, from standard materials and having standard heatexchange performance. A heat exchanger designer can utilise a chosennumber of standard heat exchanger blocks to achieve the performancerequired of the assembled heat exchanger.

There is also provided a heat exchanger block comprising a number oftubes and a number of fins, each fin having integral spacer meanslocated at a distance from the tubes. Each fin has a number of apertureswhich surround the respective tubes, the fins being separated by theintegral spacer means.

Preferably, the spacer means comprises a plurality of spacing elementscarried by the respective fins. Desirably the spacing elements aredeformations in the fin, usefully raised ribs, dimples or tongues of thefin material. The fins are ideally arranged in an alternating sequencewith a series of first fins interspersed with a series of second fins,the spacing elements of the first fins being out of alignment with thespacing elements of the second fins.

Preferably, the spacing elements each have a contact part which is outof alignment with the plane of the fin, and at least one support wallconnected to the contact part. Ideally the support wall is substantiallyperpendicular to the plane of the fin. The provision of substantiallyperpendicular support walls enables the spacing elements to provide goodsupport for the adjacent fins as the fins are moved along the tubes.

The support walls can be aligned substantially parallel to the flowdirection of the coolant in use, whereby the support walls do notpresent a significant barrier to the passage of the coolant, andtherefore do not significantly increase the pressure drop across theheat exchanger. Alternatively, the support walls may be aligned acrossthe flow direction whereby to induce turbulence into the coolant. Thesize and position of the spacing elements, and in particular theirsupport walls, can be chosen by the heat exchanger designer to satisfythe heat exchange and pressure drop requirements.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be further described, by way of example, withreference to the accompanying drawings, in which:

FIG. 1 shows a perspective view of a first embodiment of machine formanufacturing a heat exchanger block according to the present invention;

FIG. 2 shows a perspective view of a second embodiment of machine formanufacturing a heat exchanger block according to the present invention;

FIG. 3 shows a front view of a fin and integral spacer means of thepresent invention;

FIG. 4 shows a front view of a fin and integral spacer means which iscomplementary to that of FIG. 3;

FIG. 5 shows a front view of another fin and integral spacer means ofthe present invention;

FIG. 6 shows a front view of a fin and integral spacer means which iscomplementary to that of FIG. 5;

FIG. 7 shows an enlarged view of some of the fins of FIGS. 5 and 6;

FIG. 8 shows a plan view of a stack of fins of FIGS. 5 and 6 prior toassembly into a heat exchanger block; and

FIG. 9 shows an enlarged view of a part of the machine of FIG. 1.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

FIG. 1 shows a machine 10 for making a heat exchanger block, part ofwhich heat exchanger block is represented by the numeral 12. In knownfashion, the heat exchanger block 12 comprises a number of fins 14 and anumber of tubes 16, the fins being in thermal engagement with the tubes.

In the embodiments of FIGS. 1 and 2, the heat exchanger block 12comprises an array of tubes 16 arranged in multiple rows, whereas theheat exchanger block created from the fins of FIGS. 3-8 comprises asingle row of fins. The number of rows of tubes in the heat exchangerblock, as well as the number of tubes 16, and the number and spacing ofthe fins 14, can vary according to the heat exchange requirements.

The machine 10 of FIG. 1 and the machine 110 of FIG. 2 both comprise abase plate 20 which can rest upon, or be secured to, the floor. The baseplate 20 carries four substantially vertical support posts 22, which areconnected together at their tops by a top frame 24. The base plate 20,the support posts 22 and the top frame 24 together comprise a rigidstructure.

Mounted upon the base plate 20 is a tube-mounting plate 26. Thetube-mounting plate 26 is mounted upon resilient bushes 28 (FIG. 9)which are designed to mechanically isolate the tube-mounting plate 26from the base plate 20, for the purpose described below.

The tube-mounting plate 26 has a carrier 30 which has an array ofrecesses or openings (not shown), each of which can accommodate the endof a respective tube 16. The desired array of tubes 16 can therefore bemounted upon the carrier 30, with their longitudinal axes substantiallyparallel and vertical.

A movable top plate 32 is mounted upon the posts 22 by way of respectivesets of cam follower bearings 34, which permit the top plate to be movedup and down along the posts 22.

A pair of vibrators 36 is mounted upon the tube-mounting plate 26 in theembodiment of FIG. 1. In the alternative embodiment of FIG. 2 a similarpair of vibrators 136 is mounted upon the top plate 132. Apart from thedifferent location of the vibrators 36, 136, the embodiments of FIGS. 1and 2 are substantially identical.

The vibrators 36 and 136 each contain an electric motor which isconnected to an eccentric weight (not seen). As the electric motor isrotated the eccentric weight is caused to rotate and the eccentricitycauses the vibrator to vibrate with the frequency of the motor. It isarranged that the rate of rotation of the motor is variable whereby thefrequency of the induced oscillations can be varied to match therequirements of the particular heat exchanger block 12. In oneembodiment, the motor rotates at 3,000 rpm, providing vibrations with afrequency of 50 Hz.

The tube-mounting plate 26 is mechanically isolated from the base plate20 so as to reduce, and ideally minimise, the vibrations which pass tothe base plate 20 and to the underlying floor.

In order to assemble a heat exchanger block 12 the desired array oftubes 16 is mounted onto the carrier 30. A stack of fins 14, comprisinga chosen number of fins which can be mounted together onto the tubes 16,is located adjacent to the top ends of the tubes. As shown in thealternative embodiments of FIGS. 3-8, each of the fins has an array ofapertures 40 which are positioned to match the array of tubes 16 in theparticular heat exchanger block, each aperture 40 being an interferencefit upon a respective tube.

The top end of each tube 16 is fitted with a tapered member (not seen)which is smaller than the aperture 40 in the fins 14, whereby the stackof fins can be placed over the tapered members prior to movement alongthe tubes.

It can be arranged that the “stack” of fins comprises a single fin, i.e.a single fin is moved along (down) the tubes at a time, but preferablythe stack comprises a plurality of fins which are moved along the tubestogether. The stack of fins can be initially secured together by apreliminary brazing, welding, or gluing step and can be presented to thetubes as a single unitary block such as that shown in FIG. 8.Alternatively, the stack of fins can be mounted in a cartridge andloaded together onto the tubes, notwithstanding that the fins 14 remainseparable at that stage.

Once the stack of fins 14 has been located at the uppermost ends of thetubes 16, the top plate 32, 132 is lowered into engagement with thetop-most fin 14. As shown in FIGS. 1 and 2, the top plate 32, 132 has anopening 42 which is of a size and shape to surround the array of tubes16. However, it is arranged that the fins 14 project beyond the array oftubes, and the opening 42 is smaller than the fins, whereby the topplate 32, 132 engages the periphery of the top-most fin 14.

The motors of the vibrators 36, 136 are actuated whereupon a vibrationis induced into the fins 14 and tubes 16, the vibration effectivelyreducing the frictional engagement between the tubes 16 and fins 14sufficiently to cause the stack of fins 14 to move down the tubes 16under the influence of gravity.

In the embodiment of FIG. 1 the top plate 32 carries a pair of weights44 which increase the downwards force upon the fins 14, whereas in theembodiment of FIG. 2 the vibrators 136 provide the desired weight uponthe top plate 132.

It will be understood that in common with many prior art fins, the fins14 have a collar 46 (see the alternative embodiment of FIGS. 7 and 8)surrounding each aperture 40, the collars 46 being designed formechanical and thermal engagement with the tubes 16 in the assembledheat exchanger block 12. It is arranged that the mechanical engagementis not sufficient to prevent the stack of fins 14 being drivendownwardly by the vibration-assisted force of the top plate 32, 132, andyet is sufficient to provide a good thermal engagement required for heattransfer in the assembled heat exchanger block.

It will be understood that FIGS. 1 and 2 show one or more stacks of fins14 which have already been driven down the tubes 16 into engagement withthe carrier 30, and another stack of fins 14 adjacent to the top of thetubes 16 ready to be moved down the tubes. The fins 14 in each stack arevery closely spaced and appear as solid in FIGS. 1 and 2, but as seen inthe enlarged view of FIG. 9 comprise a number of discrete (butinterengaging) fins (see also the interengaging fins in the alternativeembodiment of FIG. 8). It will also be understood that only some of thetubes 16 are shown in FIGS. 1 and 2, so that the form of the fins 14 canbe better understood. Clearly, when the machine 10, 110 is in use arespective tube 16 would occupy each of the openings 40 of the fins 14.

The fins 14 which are used in the present invention are fins withintegral spacer means such as those of FIGS. 3-8. A first pair of finsand integral spacer means which can be used with the machine and methodof the present invention are shown in FIGS. 3 and 4, and a second pairis shown in FIGS. 5-8. In other uses of the method the fins do not haveintegral spacer means, and neighbouring fins are separated by a discretespacer, such as the corrugated spacer of our copending applicationPCT/GB2011/052054.

The fins 214 a, 214 b of FIGS. 3 and 4 each comprise a substantiallyflat sheet 50 carrying a number of spacing elements 52 a,b. In thisembodiment the spacing elements 52 a,b are deformations created bycutting the flat sheet and pressing out a tab or tongue of the material(the sheet being cut and pressed to form spacing elements similar tothat shown in the embodiment of FIG. 8). In other embodiments thespacing elements comprise wells, dimples, deformations or the likepressed from the fin material.

It is arranged that two distinct arrays of spacing elements are providedon the respective fins 214 a, 214 b, the arrays forming complementaryspacing elements 52 a and 52 b with the spacing elements 52 a of onearray being out of alignment with the spacing elements 52 b of the otherarray. The fins 214 a and 214 b are arranged in an alternating sequencewhereby the spacing elements 52 a each engage a substantially flat (orundeformed) part of the fin 214 b, and vice versa. In this way, thespacing elements 52 a and 52 b will act to separate the adjacent fins214 a,b by a predetermined distance corresponding to the height h of thespacing elements (FIG. 8).

The form of the fins 314 a, 314 b in the alternative embodiment of FIGS.5-8 differ slightly from the fins 214 a,b. Specifically, there are fewerof the respective spacing elements 52. It will be observed that the fins314 a and 314 b are identically formed and that the fin 314 b has simplybeen rotated through 180° so as to misalign the respective spacingelements 52.

The spacing elements 52, 52 a and 52 b each comprise a tab or tongue ofmaterial which has been cut and pressed from the material of the fin.The tab is pressed in such a way that the spacing elements have acontact part 56 (see FIG. 7) which engages the neighbouring fin in use.In this embodiment the contact part is a continuous wall which lies in aplane which is substantially parallel to the plane of the fins. Thecontact wall is connected to two support walls 58 which serve to spacethe contact wall from the plane of the fin.

The support walls 58 and the contact wall 56 are of U-shape, and are cutand pressed from the fin material 50. In one method of making a spacingelement 52, a pair of parallel slits is formed through the fin materialand a pressing machine presses the material between the slits out ofalignment with the remainder of the fin and into the U-shape.

It will be seen that the support walls 58 in this embodiment are notperpendicular to the plane of the fin, but instead lie at a small angleto the perpendicular. The closer the support walls are to beingperpendicular the greater they will resist deformation of the spacingelement 52 during assembly of the heat exchanger block.

When the chosen number of fins are placed together with the spacingelement of one fin engaging the adjacent fin, the fact that the supportwalls 58 are substantially perpendicular to the plane of the finsprovides maximum support for the fins, i.e. the likelihood of thespacing elements being deformed whereby to reduce the fin spacing isreduced.

It will also be observed that the spacing elements 52, 52 a, 52 b arearranged substantially across the full area of the fins 214, 314,whereby they provide full support across the fins, both as the fins aremoved along the tubes, and also during use of the assembled heatexchanger.

However, it will also be understood that the presence of the supportwalls 58 between the adjacent fins reduces the area through which thecoolant may pass, and therefore increases the pressure drop across theheat exchanger block. The pressure drop can be minimised by arrangingthe spacing elements to that the contact walls 56 are substantiallyperpendicular with the intended direction of coolant flow C representedin FIGS. 6-8. Alternatively, as in the embodiments shown in FIGS. 3-8,the contact walls are substantially aligned with the coolant flowdirection C, and therefore induce turbulence in the coolant.

The heat exchanger designer will be able to arrange the spacing elementsso that their number and orientation provides the desired amount ofturbulence whilst avoiding an unacceptable pressure drop.

As above indicated, the apertures 40 are surrounded by a respectivecollar 46. Whilst the provision of collars is not necessary for thepresent invention, they generally increase the thermal engagementbetween a fin and a tube and are therefore usually preferable. As shownin FIG. 8, the height of each collar is significantly less than theheight h of each spacer element 52, so that the collars of adjacent finsdo not interengage or nest together, which is known to increase theforce required to move the fins along the tubes. Alternatively stated,in the present invention the separation of adjacent fins is determinedentirely by the spacer means which are located at a distance from thetubes.

It will be understood that the vibration-induced movement of the fins 14(or more properly the stack of fins 14 which are located together) alongthe tubes will terminate when the fins engage either the carrier 30, orthe top-most fin of a previously fitted stack of fins such as that shownin FIGS. 1 and 2. The spacing between each fin in each stack, andbetween the fins of adjacent stacks of fins, is determined entirely bythe spacer means, and not by any part of the machine 10, 110 itself.

When a stack of fins 14 has been moved into engagement (either with thecarrier 30 or with a previously fitted stack of fins), the vibrators 36,136 are switched off and the top plate is lifted to clear the top of thetubes for the insertion of the next stack of fins, whereupon theprocedure is repeated.

Importantly, in the embodiments of FIGS. 1 and 2 there is no requirementfor the top plate to be driven along the posts 22, in either the upwardsor downwards direction, and the downwards movement of the top plate ispreferably dependent only upon the force of gravity, and the upwardsmovement by a separate crane or lifting device (not shown). Theinvention does not, however, exclude the possibility of a pressingmachine to move the fins, in conjunction with the vibration provided byvibrators such as 36, 136. Thus, the invention can be performed with thetubes substantially horizontal, with the force to move the fins beingprovided by a pressing machine (which may be hydraulically,pneumatically or electrically actuated, as desired). The vibration ofthe tubes and fins will nevertheless assist the pressing machine byreducing the force required to move the fins along the tubes.

It will be understood that the invention could also be performed withthe fins being held stationary and the tubes being moved therethrough,and also with both of the fins and tubes being movable.

The frequency of the oscillations of the vibrators 36, 136 can be varied(during movement of the fins if desired) so as to facilitate movement ofthe fins along the tubes. Thus, it is expected that a particular form ofheat exchanger block (comprising a particular number and array of tubes,and a particular form of fins), may require a unique vibration frequencyto achieve the desired manufacturing efficiency.

If desired, one or both of the end-most fins (i.e. the bottom andtop-most fins of a vertically-aligned heat exchanger block), can be ofharder material than the remaining fins, for the purpose of reducing thelikelihood of damage to the heat exchanger block during subsequenttransportation and the assembly procedure.

In the claims:
 1. A fin (14; 214 a, 214 b; 314 a, 314 b) for a heatexchanger block (12), the fin having integral spacer means (52; 52 a, 52b) whereby the spacer means of one fin can engage the neighbouring finand determine the spacing therebetween, the fin having a number ofapertures (40) to receive a number of tubes (16), the spacer means beinglocated at a distance from the apertures.
 2. A fin (14; 214 a, 214 b;314 a, 314 b) for a heat exchanger block (12) according to claim 1 inwhich the spacer means comprises a plurality of spacing elements carriedby the fin.
 3. A fin (14; 214 a, 214 b; 314 a, 314 b) for a heatexchanger block (12) according to claim 2 in which the spacing elementsare deformations in the fin.
 4. A fin (14; 214 a, 214 b; 314 a, 314 b)for a heat exchanger block (12) according to claim 2 in which thespacing elements each have a contact part which is out of alignment withthe plane of the fin, and at least one support wall connected to thecontact part.
 5. A fin (14; 214 a, 214 b; 314 a, 314 b) for a heatexchanger block (12) according to claim 4 in which the support wall issubstantially perpendicular to the plane of the fin.
 6. A fin (14; 214a, 214 b; 314 a, 314 b) for a heat exchanger block (12) according toclaim 1 having a respective collar surrounding each of the apertures,the height (h) of the spacer means (52; 52 a, 52 b) being greater thanthe height of the collar.
 7. A heat exchanger block (12) comprising anumber of fins (14; 214 a, 214 b; 314 a, 314 b) according to claim 1mounted upon a number of tubes (16), each fin having integral spacermeans (52; 52 a, 52 b) located at a distance from the tubes.
 8. A heatexchanger block (12) according to claim 7 in which the number of finscomprises a number of first fins (214 a; 314 a) and a number of secondfins (314 a, 314 b), the fins being arranged in an alternating sequencewith a first fin located between two second fins and a second finlocated between two first fins, the spacing elements (52; 52 a) of thefirst fins being out of alignment with the spacing elements (52; 52 b)of the second fins.
 9. A method of manufacturing a heat exchanger block(12) comprising a number of tubes (16) and a number of fins (14; 214 a,214 b; 314 a, 314 b), neighbouring fins being separated by apredetermined spacing by way of spacer means (52; 52 a, 52 b), themethod including the steps of: locating a predetermined number of tubesin a chosen array; locating a number of fins adjacent an end of thetubes; fitting the fins onto the tubes; and vibrating the tubes and/orthe fins during the step of fitting the fins onto the tubes.
 10. Themethod according to claim 9 in which the tubes are oriented with theirlongitudinal axes substantially vertical whereby gravity acts to movethe fins along the tubes.
 11. The method according to claim 10 in whichgravity is the only force acting to move the fins along the tubes. 12.The method according to claim 9 in which the fins (14; 214 a, 214 b; 314a, 314 b) have integral spacer means (52; 52 a, 52 b) which maintain adesired separation between adjacent fins.